1. Field of the Invention
The present invention relates generally to apparatus and methods for servicing baghouse filters. More particularly, my invention relates to a method and a power tool for automatically extracting filter bags from baghouse tubesheets when such baghouse filtering systems are routinely serviced.
2. Description of the Prior Art
As will be recognized by those skilled in the art, a variety of baghouses are employed to filter particulates entrained in exhaust gases expelled from various commercial processes. Typical baghouses include a large enclosure having an upper gas output compartment separated from a lower gas intake compartment by a generally planar tube sheet. The rigid, usually steel tube sheet includes a plurality of orifices for receiving multiple bag air filters. The bag air filters collectively filter gases drawn from the lower compartment. The filters may comprise cartridge filters, or snap band pulse jet dust collectors. Typically these individual baghouse filters are elongated and generally tubular. An interior, generally tubular cage provides a supporting skeleton. The cage framework is surrounded by suitable fabric that provides the filtering media. The upper end of the fabric may be folded about the periphery of a mounting header that aids in suspending the bag from the tube sheet.
Typical snap band pulse jet dust collectors include a resilient band that circumscribes their diameter. The somewhat flexible band has a central, circumferential channel that is deformed somewhat during installation within a suitable tube sheet mounting orifice. As the filter is pushed into the tubesheet orifice and properly positioned, the snap band firmly seats within the orifice. In other words the band "snaps back" to flushly lock itself within the mounting orifice to seal the leak path that might otherwise occur. The cage and the fabric body drop downwardly into the air intake compartment, firmly suspended from the tubesheet by the header. In operation, gases pass through the fabric filter media, and they exit the header into the upper baghouse compartment, usually through a metallic venturi coaxial with the header.
Dust, particulate matter, and accumulated oils and residue collect on the baghouse filters, eventually degrading or interrupting gas flow. Baghouses (and their filters) must therefore be serviced regularly. Maintenance requirements are dependent upon a number of variables, including the type and volume of effluent being filtered, the nature of the particulates and chemicals borne by the air stream, the capacity of the baghouse, and the duration of operation. Some baghouses are "self cleaning." The latter systems employ blow tubes that periodically pulse the bag filters with high pressure air. Bursts of air impinging upon the bag filters partially dislodge accumulated dust and debris, which may exit the bottom of the baghouse. However, automatic self-cleaners cannot remove all of the residue that accumulates on the filter bags. As a result the bags must be periodically changed. A typical work crew uses a haphazard variety of tools for this purpose, and the process is slow and labor intensive.
For example, it is not unusual for a team of workman to employ various wedges, pry bars and other typical hand tools when changing filters. The lack of customized tools for the process contributes to the labor intensive quality of the operation. By way of example, six workman can usually remove approximately eighteen hundred individual filters after twelve to sixteen hours of manual labor. Another problem is baghouse filter damage. When conventional tools or processes are utilized to remove baghouse filters, the cages are often bent or ruined. Sometimes the bag filters are rendered completely unusable during extraction. On the other hand, if only minor damage has occurred, the baghouse filters may be serviced and rebuilt according to the teachings, for example, of U.S. Pat. No. 5,398,386 for which I was a coinventor.
Thus, there is a need for removing baghouse filters in a quick and efficient manner. Such a system should minimize manual labor and should enable a smaller team of workers to much more rapidly extract the baghouse filters. A preferred system should be cost efficient. I have found by experiment that normal labor times associated with conventional baghouse servicing can be cut by more than half with the tools or methods of my invention.